The use of optical fibers in information and communication systems is becoming increasingly popular due to their performance and transmission properties. The performance of the optical fibers depends on the purity by which they can be made and is directly proportional to the amount of losses which occur in the transmission of information through the fibers. Low losses and long lengths are very much desired.
Silica glass fibers have been made using chemical vapor deposition techniques in a semi-containerless environment. In this technique, silica is deposited inside an elongated cylinder using chemical vapor deposition techniques. The cylinder is heated to melt the silica and a fiber is pulled from the inside of the melt. These silica glass fibers have losses on the order of 2.times.10.sup.-1 db/km. While this is sufficiently low for a practical optical communication network, there are considerable advantages and cost savings to be obtained could the losses be further reduced.
Fluoride glasses are attractive because of their extremely low theoretical transmission losses, particularly at infrared wave lengths. Theoretical losses for the fluoride glass fibers are on the order of 10.sup.-3 db/km, far below that of silica glass fibers.
Heretofore, the production of fluoride glass fibers has not been possible in a semi-containerless system such as that used for silica fibers because of the unavailability of suitable chemicals for reaction techniques such as chemical vapor deposition. The low viscosity of the liquid material makes fluoride fiber drawing difficult. Suitable apparatus and methods for producing fluoride glass fibers with a high degree of purity have not been provided heretofore.
Accordingly, an important object of the present invention is to provide a method and apparatus for producing high purity optical fibers.
Still another important object of the present invention is to provide a method and apparatus for producing high purity fibers of fluoride and other glass forming materials.
Still another important object of the present invention is to provide a method and apparatus for producing glass fibers in a containerless environment to increase the purity of the fibers.
Yet another important object of the present invention is to provide a method for melting and forming optical glass fibers in which physical contact of the melt with container walls is completely avoided during the entire process.